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Results for “Predatory Behavior”

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PubMed1995

Induction of muricidal behavior by ACTH or adrenalectomy in young male Wistar rats.

ACTH administered IP induces a muricidal behavior in 52% of male Wistar rats that do not express it before; such behavior is also observed spontaneously in 68% of adrenalectomized animals. This change in behavior is characterized by an exceptionally long duration (several months in some animals), and by its prevention by previous or substitutive treatments with dexamethasone. Data obtained using hypophysectomized or adrenalectomized animals with or without ACTH treatments suggest that the muricidal-inducing effect of ACTH might have, at least partially, a central origin.

Adrenal Glands↗

PubMed2004

Predator mixes and the conspicuousness of aposematic signals.

Conspicuous warning signals of unprofitable prey are a defense against visually hunting predators. They work because predators learn to associate unprofitability with bright coloration and because strong signals are detectable and memorable. However, many species that can be considered defended are not very conspicuous; they have weak warning signals. This phenomenon has previously been ignored in models and experiments. In addition, there is significant within- and among-species variation among predators in their search behavior, in their visual, cognitive, and learning abilities, and in their resistance to defenses. In this article we explore the effects of variable predators on models that combine positive frequency-dependent, frequency-independent, and negative frequency-dependent predation and show that weak signaling of aposematic species can evolve if predators vary in their tendency to attack defended prey.

Animals↗

PubMed2006

Signaling to the enemy? Body pattern expression and its response to external cues during hunting in the cuttlefish Sepia officinalis (Cephalopoda).

Cuttlefish can rapidly alter their appearance by using neurally controlled chromatophore organs. This ability may provide a window into their cognitive capacity. We test whether the changes in body pattern that occur during hunting depend on context. If they do, then it may be possible to use these changes to study cephalopod cognition while the animal is engaged in ecologically relevant tasks. We found consistent individual differences in the tendency of cuttlefish to hunt with the first two arms raised. We also found that cuttlefish usually darken their skin after they seize a prey item. This darkening is observed regardless of the identity of the prey (fish, crab, or shrimp), prey context (buried in sand, in a bare tank, or on top of a rock pile), or the presence of a sudden stimulus. The sudden stimulus was created by presenting an overhead model bird to the cuttlefish. The model induced components of the Deimatic Display, which is a form of antipredator behavior, suggesting that the model was perceived as a potential threat. Passing Cloud displays and the Darkening of the arms were significantly reduced after exposure to the model bird. The effect of a potential predator on body pattern expression during hunting suggests it may be possible to use these changes as a sensitive indicator of ecologically relevant learning.

Animal Communication↗

PubMed2004

Differences in prey capture in grass shrimp, Palaemonetes pugio, collected along an environmental impact gradient.

The waterways and associated salt marshes along the western border of Staten Island, New York (Arthur Kill) have long been under environmental duress. Environmental threats include industrial and municipal discharges, oil spills, and possible leachate from landfills. These impacts are compounded due to the low flushing of this body of water. Grass shrimp, Palaemonetes pugio, inhabiting the Arthur Kill are, therefore, potentially at risk of exposure to metal and organic pollutants. Successful prey capture (of live brine shrimp, Artemia franciscana) was used to compare the relative health of shrimp collected from three sites along an environmental impact gradient. Study sites included a relatively unimpacted harbor (Great Kills Harbor, GK) and two creeks adjoining the Arthur Kill (Nassau Creek, NC, and Richmond Creek, RC). Shrimp originating from GK exhibited a rate of prey capture (6.3 prey h(-1)) that was about two times greater (p < 0.05) than that of shrimp originating from a creek behind a series of landfills (RC, 3.2 prey h(-1)). The rate of prey capture for shrimp collected from a creek impacted by historic smelting activities (NC) was intermediate (5.4 prey h(-1)). Laboratory studies with shrimp from a pristine site (Tuckerton, NJ) exposed to RC conditions (i.e., sediment and water) for eight weeks indicate that reduced prey capture can be induced in healthy shrimp. Finally, video analysis suggests that reduced prey capture in RC shrimp may not be the result of less effort, but rather the combination of (1) 80% fewer (p < 0.05) prey being captured with a lunge type of attack and (2) a greater reliance (p < 0.05) on a less efficient grab type of foraging behavior (64% success rate for RC versus 87% success rate for GK; p = 0.058). These results indicate that sublethal toxicity in environmentally impacted populations can occur and that prey capture may be used to assay the relative health of field specimens. Additionally, impaired prey capture may have important implications for the energy flow within impacted environments.

Animals↗

PubMed2000

Are large complex ecosystems more unstable? A theoretical reassessment with predator switching.

Multi-species Lotka-Volterra models exhibit greater instability with an increase in diversity and/or connectance. These model systems, however, lack the likely behavior that a predator will prey more heavily on some species if other prey species decline in relative abundance. We find that stability does not depend on diversity and/or connectance in multi-species Lotka-Volterra models with this 'predator switching'. This conclusion is more consistent with several empirical observations than the classic conclusion, suggesting that large complex ecosystems in nature may be more stable than previously supposed.

Animals↗

PubMed2001

Cue and context conditioning of defensive behaviors to cat odor stimuli.

Exposure of rats to a cat odor block in a previously familiarized situation was followed by three extinction days to the same or a different situation, and with or without an identical but odor-free block, and, testing in the original apparatus with an odor-free block (cue). Initial exposure produced risk assessment (stretch attend), avoidance of the block, and crouch/freeze with sniffing/head movements. Avoidance continued during extinction, but context-only exposed rats showed predominantly crouch/freeze with sniff/head movements, while rats exposed to the context+cue showed higher levels of stretch attend. During the test day, rats exposed to the cue during extinction showed reduced defensive responding compared to those not extinguished with the cue, but context extinction had less effect, possibly due in part to initial familiarization with the situation. These data indicate that both cue and context conditioning to cat odor did occur, and that the type of conditioned stimulus (context-only vs. context+cue) influenced the type of defensive behaviors elicited by this stimulus, although the all animals received the same conditioning protocol. Particular behaviors disappeared at different rates during extinction, with avoidance the most persistent. However, in this context there was no incentive for approach behaviors inconsistent with avoidance, and stretch attend behaviors could and did occur while subjects were located far from the block or the area in which it had been encountered. In addition, immobile crouch/freeze did not occur at higher than control levels, while the crouch/freeze activities that did increase incorporated sensory sampling in a relevant modality (sniffing/head movements). Thus, the behaviors seen to the conditioned stimulus appeared to reflect combinations of different defense strategies, appropriate to the type of conditioned stimulus and responsive to its extinction. Differences between these data and those from studies using fecal predator odorants suggest that the latter may not elicit a complete range of conditioned defenses.

Aggression↗

PubMed2001

Auditory scene analysis by echolocation in bats.

Echolocating bats transmit ultrasonic vocalizations and use information contained in the reflected sounds to analyze the auditory scene. Auditory scene analysis, a phenomenon that applies broadly to all hearing vertebrates, involves the grouping and segregation of sounds to perceptually organize information about auditory objects. The perceptual organization of sound is influenced by the spectral and temporal characteristics of acoustic signals. In the case of the echolocating bat, its active control over the timing, duration, intensity, and bandwidth of sonar transmissions directly impacts its perception of the auditory objects that comprise the scene. Here, data are presented from perceptual experiments, laboratory insect capture studies, and field recordings of sonar behavior of different bat species, to illustrate principles of importance to auditory scene analysis by echolocation in bats. In the perceptual experiments, FM bats (Eptesicus fuscus) learned to discriminate between systematic and random delay sequences in echo playback sets. The results of these experiments demonstrate that the FM bat can assemble information about echo delay changes over time, a requirement for the analysis of a dynamic auditory scene. Laboratory insect capture experiments examined the vocal production patterns of flying E. fuscus taking tethered insects in a large room. In each trial, the bats consistently produced echolocation signal groups with a relatively stable repetition rate (within 5%). Similar temporal patterning of sonar vocalizations was also observed in the field recordings from E. fuscus, thus suggesting the importance of temporal control of vocal production for perceptually guided behavior. It is hypothesized that a stable sonar signal production rate facilitates the perceptual organization of echoes arriving from objects at different directions and distances as the bat flies through a dynamic auditory scene. Field recordings of E. fuscus, Noctilio albiventris, N. leporinus, Pippistrellus pippistrellus, and Cormura brevirostris revealed that spectral adjustments in sonar signals may also be important to permit tracking of echoes in a complex auditory scene.

Animals↗

PubMed2005

Periodicity of mass extinctions without an extraterrestrial cause.

We study a lattice model of a multispecies prey-predator system. Numerical results show that for a small mutation rate the model develops irregular long-period oscillatory behavior with sizeable changes in a number of species. The periodicity of extinctions on Earth was suggested by Raup and Sepkoski [Proc. Natl. Acad. Sci. 81, 801 (1984)], but thus far is lacking a satisfactory explanation. Our model indicates that this might be a natural consequence of the ecosystem dynamics and not the result of any extraterrestrial cause.

Animals↗

PubMed1985

Sonar tracking of horizontally moving targets by the big brown bat Eptesicus fuscus.

When following a moving target, echolocating bats (Eptesicus fuscus) keep their heads aimed at the target's position. This tracking behavior seems not to involve predicting the target's trajectory, but is achieved by the bat's pointing its head at the target's last known position. The bat obtains frequent position updates by emitting sonar signals at a high rate. After the lag between head and target positions and the nonunity tracking gain were corrected for, bats' tracking accuracy in the horizontal plane was +/- 1.6 degree.

Animals↗

PubMed2006

Density dependence in marine fish populations revealed at small and large spatial scales.

Experimental manipulation of population density has frequently been used to demonstrate demographic density dependence. However, such studies are usually small scale and typically provide evidence of spatial (within-generation) density dependence. It is often unclear whether small-scale, experimental tests of spatial density dependence will accurately describe temporal (between-generation) density dependence required for population regulation. Understanding the mechanisms generating density dependence may provide a link between spatial experiments and temporal regulation of populations. In this study, I manipulated the density of recently settled kelp rockfish (Sebastes atrovirens) in both the presence and absence of predators to test for density-dependent mortality and whether predation was the mechanism responsible. I also examined mortality of rockfish cohorts within kelp beds throughout central California to evaluate temporal (between-generation) density dependence in mortality. Experiments suggested that short-term behavioral responses of predators and/or a shortage of prey refuges caused spatial density dependence. Temporal density dependence in mortality was also detected at larger spatial scales for several species of rockfish. It is likely that short-term responses of predators generated both spatial and temporal density dependence in mortality. Spatial experiments that describe the causal mechanisms generating density dependence may therefore be valuable in describing temporal density dependence and population regulation.

Animals↗

PubMed2000

Stochastic resonance enhances the electrosensory information available to paddlefish for prey capture.

Recent behavior experiments have demonstrated that paddlefish can make use of stochastic resonance while feeding on Daphnia plankton. Here we calculate the information content of the noisy Daphnia signal at the paddlefish rostrum using an exact statistical treatment of threshold stochastic resonance as a minimal neural model. These calculations compare well with experimentally obtained data on paddlefish strikes at Daphnia prey.

Animals↗

PubMed1993

Global behavior of n-dimensional Lotka-Volterra systems.

The behavior of Lotka-Volterra systems is studied using as tools the results from positivity and auxiliary functions that decrease along the trajectories. One typical result is that if a decomposition of the interaction matrix into a product of a symmetric and an off-diagonal nonnegative matrix is possible, then all the trajectories either go to equilibria or cannot remain in any compact set of the interior of the positive orthant.

Animals↗

PubMed2001

Patchy environment as a factor of complex plankton dynamics.

We study the role of the diffusive interaction in plankton dynamics in a patchy environment. We use a minimal reaction-diffusion model of the nutrient-plankton-fish food chain to simulate the diffusive interaction between fish-populated and fish-free habitats. We show that such interaction can give rise to spatiotemporal plankton patterns. The plankton dynamics depend on the fish predation rate and can exhibit both regular and chaotic behavior. We show that limit cycle and chaotic attractor coexist in the system. The entire basin of attraction of the limit cycles is found to be riddled with "holes" leading to the competitive chaotic attractors. The chaotic dynamics is typical of a wide range of the fish predation rates.

Animals↗

PubMed2000

Prey pursuit and interception in dragonflies.

Perching dragonflies (Libellulidae; Odonata) are sit-and-wait predators, which take off and pursue small flying insects. To investigate their prey pursuit strategy, we videotaped 36 prey-capture flights of male dragonflies, Erythemis simplicicollis and Leucorrhinia intacta, for frame-by-frame analysis. We found that dragonflies fly directly toward the point of prey interception by steering to minimize the movement of the prey's image on the retina. This behavior could be guided by target-selective descending interneurons which show directionally selective visual responses to small-object movement. We investigated how dragonflies discriminate distance of potential prey. We found a peak in angular velocity of the prey shortly before take-off which might cue the dragonfly to nearby flying targets. Parallax information from head movements was not required for successful prey pursuit.

Animals↗

PubMed1993

Dissociation between behavioral and corticosterone responses on repeated exposures to cat odor.

Rats exposed for 5 min to a phobic stimulus (the odor of a cat) had plasma corticosterone concentrations significantly higher than those exposed to a neutral odor and than a group remaining undisturbed in the animal house. During the first exposure to cat odor the increased corticosterone was related to the avoidance behavior, measured as the time spent sheltering. After five exposures to cat odor the rats continued to avoid the odor cloth, but no longer responded with raised corticosterone levels. The results are discussed with reference to the two components of a phobic response (avoidance and disturbance), and it is suggested that the latter, reflected by changes in corticosterone, habituates more readily than the former.

Animal Communication↗

PubMed2003

Cannibalism among phytoseiid mites: a review.

Cannibalism, the killing and consumption of conspecific individuals, is a common and widespread phenomenon in the animal kingdom. Cannibalism in phytoseiid mites has been known for decades but until recently reports were mainly observational and experimental data were lacking. Recently, diverse aspects of cannibalism, such as life stage-related cannibalism and preference, nutritional benefits, the role of diet specialization, species discrimination, and kin discrimination were assessed and compared within and among diverse phytoseiid species. As a result, species of the family Phytoseiidae provide a rather well studied group with respect to cannibalism at the individual level. The present review aims at summarizing and canalizing the wealth of recent experimental data on cannibalistic phytoseiid mites and seeks to emphasize and discuss the behavioral and ecological significance of cannibalism. In an ideal case, it will stimulate studies on topics related to cannibalism that are currently underrepresented such as the consequences of cannibalism for population dynamics and species composition in a given habitat. Partitioned in six sections, the key determinants of cannibalism in phytoseiid mites are treated by extracting features that are common among species and, where applicable, by indicating the circumstances that minimize the costs and maximize the benefits of cannibalism.

Animals↗

PubMed2005

Superparasitism evolution: adaptation or manipulation?

Superparasitism refers to the oviposition behavior of parasitoid females who lay their eggs in an already parasitized host. This often yields intense competition among larvae that are sharing the same host. Why would a female oviposit in such hostile habitat instead of looking for a better quality, unparasitized host? Here we present a continuous-time model of host-parasitoid interaction and discuss alternative scenarios. This model is first used to analyze the evolution of the superparasitism behavior of a solitary proovigenic parasitoid under both time and egg limitation. Then, following the recent discovery by Varaldi et al., we allow the parasitoid to be infected by a virus that alters the superparasitism behavior of its host to enhance its own horizontal transmission. The analysis of the coevolution of this manipulative behavior with the oviposition behavior of uninfected females clarifies and quantifies the conflict that emerges between the parasitoid and its virus. The model also yields new testable predictions. For example, we expect that uninfected parasitoids should superparasite less after coevolving with the manipulative virus. More generally, this model provides a theoretical framework for analyzing the evolution of the manipulation of parasitoid life-history traits by microparasites.

Adaptation, Physiological↗

PubMed2004

How predation risk affects the temporal dynamics of avian leks: greater sage grouse versus golden eagles.

Leks often attract predators as well as mates, yet most evolutionary models have assumed that sexual selection, not predation, drives lekking behavior. We explored the influence of predation on lek dynamics using a stochastic dynamic game model based on the lek-breeding greater sage grouse (Centrocercus urophasianus) and its principal avian predator, the golden eagle (Aquila chrysaetos). The model predicts time-dependent male lek attendance as a function of factors affecting both mating success (female arrival rate, male numbers, and social status) and predation risk (eagle arrival rate and group size). Dominant males are predicted to arrive sooner and leave later than subordinates, especially if mating skew is high, predation risk is low, or the relationship between lek size and female arrival rate is weak. Both high mean levels of predation risk and small lek size should reduce lek attendance, but the relative tendency of predators to attack large versus small leks has little influence on predicted lekking behavior. Field observations confirmed the predicted effects of female arrival rate, lek size, male dominance, and weather-dependent predator arrival rates on lek departure times. Predicted effects of female arrival rates and male dominance on seasonal lek attendance were also supported. Our model provides an empirically supported adaptive explanation for short-term lek dynamics. It also suggests alternative interpretations for phenomena previously invoked to support the hotshot and skew models of lek formation.

Animals↗